Paypal api – Paypal REST API Subscription integration error

I am trying to integrate Paypal Subscriptions via PAYPAL REST API ,using the following documentation
https://developer.paypal.com/docs/subscriptions/integrate/ ( Basic Integration )

Step 1 ( Autorization succesfully )
Step 2 ( Creating Product Successfuly )
Step 3 ( Creating Plan Succesfuly )

Step 4 ( Creating subscription fail )
It look like via Smart Payment Buttons in the JavaScript SDK work . But via REST API

curl -v -k -X POST https://api.sandbox.paypal.com/v1/billing/subscriptions 
  -H "Accept: application/json" 
  -H "Authorization: Bearer Access-Token" 
  -H "PayPal-Request-Id: SUBSCRIPTION-21092020-001" 
  -H "Prefer: return=representation" 
  -H "Content-Type: application/json" 
  -d '{
        "plan_id": "P-4ML8771254154362WXNWU5BC",
        "start_time": "2020-11-01T00:00:00Z",
        "quantity": "20",
        "shipping_amount": {
            "currency_code": "USD",
            "value": "10.00"
        },
        "subscriber": {
          "name": {
              "given_name": "John",
              "surname": "Doe"
          },
          "email_address": "[email protected]",
          "shipping_address": {
              "name": {
                  "full_name": "John Doe"
              },
              "address": {
                  "address_line_1": "2211 N First Street",
                  "address_line_2": "Building 17",
                  "admin_area_2": "San Jose",
                  "admin_area_1": "CA",
                  "postal_code": "95131",
                  "country_code": "US"
              }
          }
        },
        "application_context": {
          "brand_name": "example",
          "locale": "en-US",
          "shipping_preference": "SET_PROVIDED_ADDRESS",
          "user_action": "SUBSCRIBE_NOW",
          "payment_method": {
              "payer_selected": "PAYPAL",
              "payee_preferred": "IMMEDIATE_PAYMENT_REQUIRED"
          },
          "return_url": "https://example.com/returnUrl",
          "cancel_url": "https://example.com/cancelUrl"
        }
      }'

I get

{"name":"INVALID_REQUEST","message":"Request is not well-formed, syntactically incorrect, or violates schema.","debug_id":"ec6f365217c37","details":[{"field":"/name","location":"body","issue":"MISSING_REQUIRED_PARAMETER","description":"A required field is missing."},{"field":"/payment_preferences","location":"body","issue":"MISSING_REQUIRED_PARAMETER","description":"A required field is missing."},{"field":"/billing_cycles","location":"body","issue":"MISSING_REQUIRED_PARAMETER","description":"A required field is missing."},{"field":"/product_id","location":"body","issue":"MISSING_REQUIRED_PARAMETER","description":"A required field is missing."}],"links":[{"href":"https://developer.paypal.com/docs/api/v1/billing/subscriptions#INVALID_REQUEST","rel":"information_link","method":"GET"}]}

I tyed in all possible ways but I don’t know how to debug the problem and what I am missing in create subscription request. Thank you !